Image processing device and system

ABSTRACT

In an image processing device, a white level reference value is obtained by allowing an CCD sensor to scan a white level standard sheet. The white level reference value is stored in SRAM which is resident in a scan cartridge. The white level reference value in the SRAM is modified when an original document is read through a clear sheet, to obtain a high-quality image.

BACKGROUND OF THE INVENTION

[0001] 1.Field of the Invention

[0002] The present invention relates to an image processing device andsystem, and more particularly to an image processing device and systemwhich picks up an image from an original document and processes theimage.

[0003] 2. Description of the Related Art

[0004] Typically, in a scanning operation, available scanners project alight ray onto an original to be scanned, the light ray is reflectedfrom the original and then enters optical block of the scanner, and thelevel of the light-ray is analog-to-digital converted (hereinafter A/Dconverted) into a digital value that is output as scanned imageinformation. One of the important parameters that determines the imagequality of such a scanner is contrast of the image. The contrast of theimage is defined as the range between the darkest pixel in the image andthe lightest pixel in the image. The scanner A/D converts acquiredanalog image data into digital data within the range of contrast. Thecontrast information is represented relative to white level reference,namely, digital data that is obtained when the optical system of thescanner scans a white reference surface. Specifically, when analog imagedata from each pixel is A/D converted, white reference data is used as areference.

[0005] When the scanner reads the image and the white level reference,its output is determined depending on the hardware such as a lightsource, an optical sensor, an A/D converter circuit. Also determined areposition accuracy and variations among individual scanners. When readingany given pixel, the rate of variation dependent on these factors shouldbe kept to a minimum to obtain a reliable output from the pixel and thenachieve excellent image quality. To this end, a diversity of methods areimplemented: for example, high precision components are used, the lightintensity of the light source is increased, the read time per pixel isincreased, and measurement of white level as a reference is performed ateach scanning of the original.

[0006] When the scanner scans the original through a clear sheet, lighttransmissivity of the clear sheet lowers reflectance of the original,and thus, a contrast correction circuit corrects the reflectance or thewhite level reference is updated each time a scan is completed.

[0007] When the miniature size and low cost of the scanner are dictatedby portability, space requirement, and economy considerations,components in use are subject to limitations: for example, componentshaving high precision, heat resistance, and high noise immunity, orelectric circuit containing such components, are difficult to employ.The output level of the light source cannot be increased from thestandpoint of power saving, low-cost design, and heat dissipation. Forthis reason, light sources with a small light intensity, such as alow-cost Xe lamp and an LED, are frequently used. To acquire data in areliable fashion, the read time per pixel (accumulation time per pixel)is prolonged, and the gain of the sensor is increased. These allcontribute to the increase in the cost of the scanner. Occasionally,miniaturization of the scanner results in a scanner which cannotphysically accommodate a white level measuring surface (white surface)for measuring the white level reference. In such a case, a user mustplace a white level standard sheet on an original document mount tomeasure the white level reference and scan it.

[0008] Some wordprocessors today are equipped with a serial printer inwhich a print head cartridge, as recording means, can be replaced with ascan head cartridge that is similarly sized to the print head cartridge.In this way, wordprocessors with such a scanner unit mounted canfunction as a scanner device as well.

[0009] Unlike a normal flat head scanner, a serial scanner has ascanner-unit mounted carriage that is designed to travel a relativelylong distance, and thus scan time is prolonged. Because of the long scantime, an increase of accumulation time of a sensor such as a CCD isdifficult to implement. Furthermore, acquisition of the white levelreference takes time accordingly.

[0010] When scanning is performed through a clear sheet, physicalcharacteristics of the clear sheet degrade the reading accuracy and gainof the sensor. Because of this, the serial scanner must be periodicallycalibrated in connection with the white level reference measurementusing the white level standard sheet. The serial scanner takes time tocomplete scanning, making frequent calibrations impractical andresulting in a degradation in image quality.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide a miniatureand low-cost image processing system that presents a high-quality image.

[0012] It is another object of the present invention to provide aneasy-to-use image processing device that presents a high-quality image.

[0013] To achieve the above objects, the image processing device of thepresent invention with a slidable carriage, in one embodiment, comprisesa read cartridge that is mounted on the carriage during use, saidcartridge comprising photoelectric converter means for optically readingan image from an original document and converting the image into animage signal, and memory means for storing reference data that is usedto correct the image signal output by the photoelectric converter means.

[0014] The image processing system of the present invention in anotherembodiment comprises a control device, and an image processing deviceconnected to the control device, with a slidable carriage, whichcomprises a read cartridge that is mounted on the carriage during use,said cartridge comprising: photoelectric converter means for opticallyreading an image from an original document and converting the image intoan image signal, and memory means for storing reference data that isused to correct the image signal output by the photoelectric convertermeans.

[0015] In the above arrangement, a compact read cartridge is used toread an original document, and the read image is subjected to acorrection so that a high-quality image is acquired.

[0016] These and other objects and advantages of the present inventionwill become more apparent when the following detailed description of thepresent invention is considered with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 shows generally a personal computer having a built-inserial printer/scanner block.

[0018]FIG. 2 is a block diagram of the personal computer having thebuilt-in serial printer/scanner block.

[0019]FIG. 3 is a perspective view of the serial printer/scanner block.

[0020]FIG. 4 is a block diagram of the serial printer/scanner block.

[0021]FIG. 5 is a block diagram of the serial printer/scannercontroller.

[0022]FIG. 6 shows the map of an I/O data register set of the serialprinter/scanner block.

[0023]FIG. 7 shows the organization of record data buffer area andreceive data buffer area in RAM 403.

[0024]FIG. 8 is a perspective view of a scan head cartridge.

[0025]FIG. 9 is a block diagram of the internal organization of the scanhead cartridge.

[0026]FIG. 10 shows the map of an I/O port register in the scancontroller 906 in the scan head cartridge.

[0027]FIG. 11 is a perspective view showing the optical path of thereading light ray reflected and the components of the optical system ofthe scan head cartridge.

[0028]FIG. 12 is a side view showing the optical path of the reflectedreading light ray and the components of the optical system of the scanhead cartridge.

[0029]FIG. 13 shows the optical path of the reflected reading light rayof the scan head cartridge.

[0030] FIGS. 14(a) and 14(b) show the optical section of the scan headcartridge.

[0031]FIG. 15 illustrates the movement of the scan head cartridge whenit is used to read the image.

[0032]FIG. 16 shows the accumulation time, carriage speed, and readingresolution in the scanner.

[0033]FIG. 17 is a block diagram showing dedicated status ports used forexchanging data between a host personal computer 200 and aprinter/scanner block 219 in the serial printer/scanner built-inpersonal computer system.

[0034]FIG. 18 shows the organization of dedicated status port 1 used forexchanging data between the host personal computer 200 andprinter/scanner block 219 in the serial printer/scanner built-inpersonal computer system.

[0035]FIG. 19 shows a variety of control commands for the serialprinter/scanner block.

[0036]FIG. 20 shows the organization of dedicated status port 2 used forexchanging data between the host personal computer 200 andprinter/scanner block 219 in the serial printer/scanner built-inpersonal computer system.

[0037]FIG. 21 shows the organization of dedicated status port 3 used forexchanging data between the host personal computer 200 andprinter/scanner block 219 in the serial printer/scanner built-inpersonal computer system.

[0038]FIG. 22 is a flow diagram for the correction of white levelreference data.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Referring now to the drawings, the embodiments of the presentinvention will now be discussed.

[0040] Printer/Scanner Block and its Host Personal Computer

[0041]FIG. 1 shows generally a portable personal computer system havinga built-in serial printer. FIG. 2 is a block diagram of the personalcomputer. The personal computer, equipped with a carriage that carriesthe print head cartridge of a serial ink-jet printer, is adapted tomount a scan head cartridge that has identically sized to replace theprint head cartridge, and thus the personal computer also works as ascanner for scanning or reading a document.

[0042] In the host personal computer (more simply referred to as host),a central processor unit (CPU) 201 generally controls the entirecomputer system, and its basic control program is stored in BIOS ROM202. CPU 201 reads an application program from non-volatile read/writememory such as a floppy disk (FDD) 203 or a hard disk (HDD) 204 througha floppy disk controller (FDC) 205 or a hard disk controller (HDC) 206,respectively, expands the application into the system main memory 207,and executes the application from the system main memory 207. Tovisually present an image, a video graphic array controller (VGAC) 208displays, on a liquid-crystal display (LCD) 209, characters and the likewritten in a video memory (VRAM) 210. A keyboard input from a keyboard211 is fed through a keyboard controller (KBC) 212. A floating-pointarithmetic unit (FPU) 213 supports CPU 201 in its arithmetic operation.

[0043] A real time clock (RTC) 214 presents a current elapsed time, andcontinuously operates from its dedicated battery even when power for theentire system is interrupted. An unshown SRAM memory stores systemstatus information about the status of the system. This memory is alsobacked up by the above mentioned dedicated battery and retains itscontent while power is removed. A DMA controller (DMAC) 215 performsdata transfer without CPU intervention to transfer data rapidly betweenmemory and memory, between memory and I/O, and between I/O and I/O. Aninterrupt request controller (IRQC) 216 receives an interrupt requestfrom each I/O, and executes the interrupt request according to thepriority of requests. A timer has a plurality of channels offree-running timer outputs, and performs a variety of time controls.Also included in the host are a serial interface (SIO) 217 linked to anexternal system, an extension port (PORT) 218, and LEDs (not shown) forindicating statuses to a user.

[0044] The host personal computer is connected to the serialprinter/scanner block 219. By selectively mounting either a detachableprint head or a detachable scan head on the carriage of the printer, thepersonal computer performs printing or scanning operation, respectively.

[0045] The printer is connected to the host personal computer through aparallel interface. The host personal computer and a printer controllerexchange status data and print/scan data at the register level of theI/O ports.

[0046] Printer/Scanner Block

[0047]FIG. 3 is a perspective view that shows the internal organizationof the printer/scanner block 219 of the present embodiment that employsan ink-jet recording system. FIG. 3 shows a print head cartridge 302, acarriage 305 for attaching the cartridge 302 on the printer/scannerblock, and a guide 306 for guiding the carriage 305 in the sub scandirection. A feed roller 307 advances a recording paper 3 in the mainscan direction. A paper transport motor 308 rotates the feed roller 307.The carriage 305 has a printed circuit board (not shown) which containsan electric circuit for controlling the printer and which connects to anFPC cable 309 that carries a driving pulse current signal that drivesthe print head cartridge 302 and a head temperature control current.

[0048] A driving carriage motor 310 rotates in forward or reversedirection. The carriage 305 is engaged with a carrier belt (not shown)that is driven by a drive transmission gear 3101 which rotates inresponse to the forward and reverse rotations of the carriage motor 310.The carriage 305 thus moves in directions a and b in a reciprocalfashion. A photocoupler 311 is home position sensor means which switchesthe direction of rotation of the carriage motor 310 by sensing thepresence of the carriage 305. An automatic sheet feeding (ASF) motor 312advances the recording paper 3 by means of an ASF roller (not shown)until the recording paper 3 reaches the above-described feed roller 307.

[0049]FIG. 4 is the block diagram of the printer/scanner block. Theprinter/scanner block 219 comprises CPU 401 for controlling the printer,ROM 402 for storing a printer/scanner control program, printeremulation, and print fonts, RAM 403 for storing expanded data to beprinted, image data picked up by the scanner, and data received from thehost, a print/scan head 404 for the printer/scanner, a motor driver 405for driving the motor, and a printer/scanner controller 406 forcontrolling memory access, exchanging data with the host personalcomputer, and outputting a control signal to the printer driver. Athermistor 407 is also provided to control the temperature of thehousing of the entire block.

[0050] While CPU 401 mechanically and electrically controls theprinter/scanner block according to the control program in ROM 402, itreads from I/O data register set 501 (shown in FIG. 5) in the controlleran emulation command that is fed to the printer/scanner block from thehost section, and writes and reads the control content corresponding tothe emulation command to and from the I/O data register set and the I/Oport in the printer/scanner controller.

[0051] Printer/Scanner Controller

[0052]FIG. 5 is a block diagram of the printer/scanner controller 406.

[0053] The controller 406 comprises the I/O data register set 501 forexchanging data at command level with the host, a receive buffercontroller 502 for writing the received data from the register 501directly onto RAM 403, a print/scan buffer controller 503 which, duringprinting, reads the received data from the recording data buffer in RAM403 and sends the data to the print head, and which, during scanning,writes data coming in from the scan head directly onto the recordingbuffer in RAM 403, a memory controller 504 for controlling memory accessfrom three directions to RAM 403, a print/scan sequence controller 505for controlling print/scan sequence, and a host interface 506 forcontrolling communications with the host.

[0054]FIG. 6 shows the map of the I/O data register set 501 in theprinter/scanner block. A motor control port register 601 is used tocontrol ports and drive each motor by rewriting its value.

[0055] A print buffer and heat control register 602 defines a data arearequired for print and scan operations. By setting a start address 6021and a stop address 6022 (only the start address is used duringscanning), the print/scan buffer controller 503 reads the recording datain RAM 403 within the range from the start address to the stop address,and then writes the recording data to the data buffer register. The dataaddress pointer indicates the data address of the current data beingsent or being written. During printing, the read data is transferred tothe print head, and the head driver in the print head issues the controlsignal. During scanning, the data coming from the scan head is writtenon the buffer register.

[0056] A receive buffer register 603 defines a data area required forreception. By setting a start address 6031 and a stop address 6032 (onlythe start address is used during scanning), the receive buffercontroller 502 writes the recording data in RAM 403 within the rangefrom the start address to the stop address. The data address pointerindicates the data address that has now received data. FIG. 7 shows theaddress areas for the recording data buffer and receive buffer in RAM403 in the above operations.

[0057] Scanner

[0058]FIG. 8 is a perspective view showing the scan head cartridge 800.The scan head cartridge 800 to be mounted on the printer/scanner blockin FIG. 3 is sized to replace the print head cartridge 302 used forprinting, and has a connector 801 for electric connection with theprinter/scanner block, having compatibility with the one for the printhead cartridge. The carriage 305 in FIG. 3 transmits and receivescontrol signals and scanned signals to and from the scan head cartridge800 through a contact section 802 of the connector 801. A head guide 303fastens the scan head cartridge 800 to the carriage 305. The scannedsignal and the control signal are exchanged with the printer/scannercontroller 406 of the printer/scanner block via the contact section 802and a flexible cable 304.

[0059]FIG. 9 is the block diagram showing the internal organization ofthe scan head cartridge 800 of FIG. 8. A flexible board on whichelectronic components shown are mounted is disposed inside the cartridgein a manner that the flexible board surrounds the components of aninternal optical system in a box-like configuration. Connector 801exchanges the control signal and the scanned signal with theprinter/scanner block, and reference numeral 802 designates its contactsection. An LED device 902 is a light source for illuminating anoriginal document 901, and lights when power is supplied via theconnector 801. When the light source 902 illuminates the original 901, amirror 903 re-directs the light ray reflected from the original 901toward a CCD sensor 904. The analog output that the CCD sensor 904 givesin response to the incident light ray is amplified by an amplifier 905,and then is fed to a scanner controller IC 906. IC 906 exchanges dataand commands with the printer/scanner block, outputs control signals tothe LED 902 and CCD 904 in accordance with the commands from theprinter/scanner block, and transmits the amplified analog signal fromthe CCD 904 to an A/D converter block 9061 and to the printer/scannerblock as well. A working SRAM 907 stores two types of A/D referencevalues, namely the white level reference value and offset value, as wellas the status of the scanner, while expanding the scanned data. The I/Oport registers in the scanner controller 906 exchange commands with theprinter/scanner. FIG. 10 shows the register map of the I/O port.

[0060] Reading Scanned Data

[0061] Referring to FIG. 9, the process of data reading of the scanneris discussed.

[0062] To read data, the white level reference needs to be read andstored first. The white level standard sheet is set up in a scanningposition in the same way as an ordinary original document. When thehost, shown in FIG. 2, issues a white level reference read command tothe printer/scanner block 219, the printer/scanner block 219 in turnissues a white level reference read command to the scanner controller906, while driving the motor driver 405 in FIG. 4. Driven by thecarriage motor 310, the scan head cartridge 800 scans the white levelstandard sheet in the direction of line while the paper transport motor308 advances the white level standard sheet 901 in the direction ofcolumn. The white level reference is thus read. Also, the offset data ofa dark level reference is obtained with the scanner light source LEDextinguished.

[0063] Under the control of the scanner controller 906, both theresulting white level reference data and the offset data of dark levelreference are once directly transferred to the host 200, and thentransferred from the host 200 to SRAM 907 to be stored there. Theresulting white level reference data stored in SRAM 907 is continuouslyused until power is removed or until any modification is introduced inthe operating environment of the host 200. Thus, the time required formeasuring a white level reference at each scanning is saved.

[0064] A real original document is read in the same way as the whitelevel standard sheet has been read, and the read data is stored in SRAM907. The stored data is subjected to a comparison process referencing tothe white level reference data and offset data in the scanner controller906, and then transferred to the host 200 via the printer/scanner block219, as actually read data. The comparison process comprises convertingthe read data into an expression in percentage over a full range withthe offset data set to 0% and the white level reference data set to100%.

[0065]FIGS. 11 and 12 show the arrangement of the components of theoptical system in the scan head cartridge 800 and the optical path ofthe reflected light ray. Referring to both figures, the scan headcartridge 800 will now be described.

[0066] A case 2 houses a rod lens 6 having a cylindrical configuration,as collector means. The rod lens 6 is arranged in the vicinity of LEDs 3such that it extends along the row of the LEDs 3. The axis ofillumination of the LEDs 3 passes the center of the working surface ofthe rod lens 6, and enters obliquely to the plane of the original 901.The light ray reflected from the original 901 passes through a fieldlens 7, as a first imaging lens, whose optical central axis isapproximately at a right angle to the plane of the original 901, and thelight ray is then reflected at 90° off a mirror 5 arranged in parallelwith the scan width to propagate substantially in parallel with theplane of the original 901. An aperture 11 forms an imaging plane onwhich the field lens 7 focuses the light ray. Disposed behind theaperture 11 is a second imaging lens. The imaging position of the secondimaging lens agrees with the position of a CCD sensor 13.

[0067]FIG. 13 shows the optical path of the reflected reading light rayshown in FIGS. 11 and 12. FIG. 13 shows a top view and a side view ofthe optical path of the reflected reading light ray.

[0068] The light ray is designated by 1301. A scan line 1302 representsa line of reflection 1302 at which the light ray 1301 emitted from LEDs902 is reflected off the original 901 to be read, toward a CCD sensor904.

[0069] As can be understood from FIG. 13, the light rays emitted by arow of plurality of LEDs 902 are reflected off the line of reflection1302, and collected by a receiving lens and the mirror 903, and thenreach a plurality of CCD sensors 904 arranged in a row.

[0070] Although the scan head cartridge 800 thus constructed isconvenient in implementing a miniature and low-cost design, the incidentlight ray and reflected light ray make an angle e as shown in FIG. 14(a)because the LEDs as the light source obliquely illuminate the plane ofthe original. For this reason, when the original is shifted from itsreference height level 1402 to a raised position 1403 or a loweredposition 1404, the light ray reflected off a different position on theoriginal enters the receiving lens and the mirror 903, making itimpossible for the scan head cartridge 800 to pick up the imageaccurately.

[0071] To resolve this problem, a penta prism 1401 shown in FIG. 14(b)is useful. Referring to FIG. 14(b), the light rays from the LEDs 902illuminate the plane of the original at a right angle, and the lightrays are reflected off the plane of the original at a right angle aswell. Even if the original is shifted from the reference height level1402, the reflected light rays enter the receiving lens and mirror 903in the same position, and thus the scan head cartridge 800 accuratelyreads the image.

[0072] As described above, the scan head cartridge in this embodiment isminiaturized with a small number of LEDs 902, a short receiving lens andmirror 903, a total of 128 CCD sensors 904 with sensor spacing of{fraction (1/360)} inch and a scan width of 0.36 inch.

[0073]FIG. 15 shows an operation example in which the above scanhead-cartridge 800 scans the entire surface of the original document 901to be read. The scanning operation is performed by moving the scan headof 128 CCD sensors 904 arranged in the direction of column, in thedirection of row (line). In this case, the scan width or swath in thedirection of column is only 0.6 inch. To scan the entire surface of theoriginal 901 to be read, another cycle of scan should be repeated eachtime the original 901 is fed by the scan width in succession to eachprevious scan cycle. In this embodiment, the scan head cartridge 800 isdesigned to scan a plurality of times as shown by the orbit 1501 of thescan head.

[0074]FIG. 16 lists the reading resolution of the scan head cartridgewith respect to the carriage speed and accumulation time. By theaccumulation time is meant the time required to read one pixel. Thecarriage speed means the speed of the scan head cartridge 800 in thedirection of a line. In this case, the reading resolution of the scanhead cartridge 800 is expressed by the following equation.

Reading resolution=1/(accumulation time×carriage speed)   1

[0075] The device of this embodiment is now discussed for the cases inwhich reading resolution is 360 dpi with an accumulation time of 256 μsand the reading resolution is 180 dpi with an accumulation time of 512μs.

[0076]FIG. 17 shows dedicated status ports used for exchanging databetween the host 200 and the printer/scanner block 219.

[0077] A status port 1, designated 1701, is constructed of 8 bits, andis used to exchange data concerning statuses of other status ports andthe printer/scanner block 219. A status port 2, designated 1702, isconstructed of 16 bits, and is used to exchange commands and data. Astatus port 3, designated 1703, is constructed of 16 bits, and is usedto transmit print image data from the host 200 to the printer/scannerblock 219.

[0078]FIG. 18 describes in detail the status port 1, designated 1701.Each bit can be referenced from both the host 200 and theprinter/scanner block 219.

[0079] Bit 0 at 1801 is 1 when the host 200 is sending data to theprinter/scanner 219 via the status port 2 at 1702, and is 0 when thehost 200 is not sending. Bit 1 at 1802 is 1 when the printer/scannerblock 219 is sending data to the host 200 via the status port 2 at 1702,and is 0 when the printer/scanner block 219 is not sending. Bit 2 at1803 is 0 when data transfer is enabled from the host 200 to theprinter/scanner block 219 via the status port 3 at 1703, and is 1 whendata transfer is disabled. Bit 3 at 1804 is 0 when the printer/scannerblock 219 is powered, and is 1 when the printer/scanner block 219 is notpowered. Bit 4 at 1805 is 1 when the printer/scanner block 219 is busy,and is 0 when the printer/scanner block 219 is ready. Bit 5 at 1806 is 1when initialization of the status ports 1701-1703 is in progress, and is0 when the status ports 1701-1703 are already initialized.

[0080]FIG. 19 is a table of commands the host 200 sends to theprinter/scanner block 219 via the status port 2 at 1702. The host 200writes these commands on the status port 2 at 1702, and sets the flag atthe bit 0 at 1801. Upon detecting the flag set at the bit 0 at 1801, theprinter/scanner block 219 performs a process in accordance with thecommand written onto the status port 2 at 1702 and then resets the flagat the bit 0 at 1801. When the printer/scanner block 219 completes theprocess, it writes the result of the process to the status port 2 at1702, setting the flag at the bit 1 at 1802. Upon detecting the flag atthe bit 1 at 1802, the host 200 reads the content of the status port 2at 1702, and resets the flag at the bit 1 at 1802 when the reading iscompleted.

[0081] The commands will now be discussed in detail. 1000H at 1901initializes the status ports 1, 2, and 3.

[0082] 4000H at 1902 transfers a print image. After writing thiscommand, printing is accomplished by writing the image data itself ontothe status port 3 at 1703. 8000H-8F78H at 1903 is a command for readingthe scanner. Its lower 12 bits represent a feed amount after a scanningoperation of an image. When the command is written, the image data readis sequentially sent from the printer/scanner block 219 to the host 200via the status port 2 at 1702. After the image data is transferred, thefeed amount indicated by the lower 12 bits is fed, and the readingoperation is completed. A unit of the feed amount equals {fraction(1/360)} inch.

[0083] 9000H-9F78H at 1904 is a command for specifying the feedoperation. Its lower 12 bits specify the feed amount. Unit of the feedamount is {fraction (1/360)} inch.

[0084] 9FF0H at 1905 is a command for discharging the paper.

[0085] 9FF1H at 1906 is a command for feeding the paper.

[0086] A801H at 1907 is a command for collecting the information aboutthe head currently mounted on the printer/scanner block 219. When thiscommand is issued, the head information of 1 byte shown in FIG. 20 issent from the printer/scanner block 219 to the host 200 via the statusport 2 at 1702. Bit 0 at 2001 in FIG. 20 indicates the type of headcurrently mounted on the printer/scanner block 219. When it is 0, thescan head is now mounted. When it is 1, the print head is now mounted.Bit 1 at 2002 indicates whether any head is mounted on theprinter/scanner block 219. When it is 0, no head is mounted, and when itis 1, a head is mounted.

[0087] A805H at 1908 in FIG. 19 is a command for collecting theinformation about the reading resolution setting set in theprinter/scanner block 219. When this command is issued, theprinter/scanner block 219 sends to the host 200 the information of 1byte indicating the reading resolution as shown in FIG. 21. As shown,when bit 0 at 2101 in FIG. 21 is 1, the reading resolution is 360 dpi.When bit 1 at 2102 is 1, the reading resolution is 180 dip, and when bit2 at 2103 is 1, the reading resolution is 90 dpi. No more than one bitcan be 1 at any one time.

[0088] AD00H-AD3FH at 1909 is a command for collecting the white levelreference value detected at the accumulation time setting of 512 μs. Thelower 8 bits correspond to dots 0-127. Upon receiving this command, theprinter/scanner block 219 issues 1 byte of the white level referencevalue at a respective dot to the host 200 via the status port 2 at 1702.

[0089] AD40H-AD7FH at 1910 is a command for collecting the white levelreference value detected at the accumulation time setting of 256 μs.Lower 8 bits correspond to dots 0-127. Upon receiving this command, theprinter/scanner block 219 issues 1 byte of the white level referencevalue at a respective dot to the host 200 via the status port 2 at 1702.

[0090] AD80H at 1911 is a command for collecting the ID of the head.Upon receiving the command, the printer/scanner block 219 sends the IDof the head to the host 200 via the status port 2 at 1702.

[0091] AD81H at 1912 is a command for collecting the information of theinternal temperature inside the printer/scanner block 219. Uponreceiving this command, the printer/scanner block 219 sends 1 byteinternal temperature information to the host 200 via the status port 2at 1702.

[0092] ADF0H at 1913 is a command for executing the measurement of thewhite level reference. Upon receiving this command, the printer/scannerblock 219 performs the measurement of the white level reference at eachof the accumulation time settings of 512 μs and 256 μs.

[0093] B805H at 1914 is a command for setting a new reading resolution.A new reading resolution is set by sending reading resolutioninformation of 1 byte as shown in FIG. 20 to the printer/scanner block219 in succession to this command.

[0094] BD00H at 1915 is a command for sending the white level referencevalue at the accumulation time setting of 512 μs from the host 200 toRAM 403 in the printer/scanner block 219. Its lower 8 bits correspondsequentially to head dots 0-127. The white level reference value of eachrespective dot is set by sending the white level reference value of 1byte to the printer/scanner block 219 in succession to this command. Thewhite level reference value in RAM 403 is written onto SRAM 907 in thescan head prior to the real scanning operation.

[0095] BD40H-BD7FH at 1916 is a command for sending the white levelreference value at the accumulation time setting of 256 μs from the host200 to RAM 403 in the printer/scanner block 219. Its lower 8 bitscorrespond sequentially to head dots 0-127. The white level referencevalue of each respective dot is set by sending the white level referencevalue of 1 byte to the printer/scanner block 219 in succession to thiscommand. The white level reference value in RAM 403 is written onto SRAM907 in the scan head prior to the real scanning operation. Although thewhite level reference value is set herein based on the accumulationtime, alternatively the white level reference value may be set based onthe reading resolution.

[0096] BDF0H at 1917 is a command for writing the white level referencevalue in RAM 403 in the printer/scanner block 219, onto the scan head.

[0097] D000H at 1918 is a command for moving the carriage to its headreplacement position. Upon receiving the command, the printer/scannerblock 219 initializes the head and then moves the carriage to its homeposition.

[0098] D100H at 1919 is a command for returning the carriage from itsread replacement position to its home position. Upon receiving thiscommand, the printer/scanner block 219 initializes the head and movesthe carriage to its home position.

[0099] Correcting White Reference Data

[0100]FIG. 22 is the flow diagram for the correction sequence of thewhite reference data. The correction procedure will now be discussedwith reference to FIG. 22.

[0101] A reading operation starts at step 2201 in FIG. 22. At step 2202,the white reference measurement flag F1 is referenced. When the whitereference measurement flag F1=1, and thus a Y (yes) condition ispresent, the sequence goes to step 2204. When the flag F=0, a N (No)condition, the sequence goes to step 2203 to measure the white levelreference value. At step 2203, the white reference measurement starts.At step 22031, the host 200 issues the command 1913 “execute measurementof white level reference value” in FIG. 19 for detection of the whitelevel reference. At step 22032, in response to the command 1909/1910“read white level reference,” the white level reference value measuredby the scan head cartridge 800 is sent to the host 200. At step 22033,the host 200 issues the command 1915/1916 “set white level referencevalue” for setting the white level reference value to store the whitelevel reference value in RAM 403 in the printer/scanner block 219. Atstep 22034, the printer/scanner block 219 writes the white levelreference value onto SRAM 907 in the scan head cartridge 800 in responseto the command 1917 “execute setting of white level reference” forwriting the white level reference value. After these steps, the whitereference measurement flag F1 is set to “1.” The sequence returns tostep 2202 via (1).

[0102] At step 2204, a determination is made of whether the clear sheetis used. When it is not used, the sequence goes to step 2208. When it isused, the sequence goes to step 2205, where a clear sheet correctionflag F2 is checked. At step 2205, the sequence goes to step 2211 via (2)when F2=1. When F2=0, the sequence goes to step 2206. The white levelreference value correction starts at step 2206. At step 22061, the host200 compresses the white level reference value at a predetermined ratio,and regards it as a clear sheet white level reference value. At step22062, the corrected clear sheet white level is written onto SRAM 907 inthe scan head cartridge 800 according to the commands 1915/1916 “setwhite level reference value” and the command 1917 “execute setting ofthe white level reference.” Finally, the clear sheet correction flag F2is set to “1,” at step 2207, and then the sequence goes to (2).

[0103] If the clear sheet is not being used, the sequence goes to step2208, where the clear sheet correction flag F2 is checked to determinewhether the clear sheet was used previously. When it was not used, thatis, when F2=0, the sequence goes to (2). When it was used, that is, whenF2=1, the sequence goes to step 2209. At step 2209, to put the clearsheet white level back to the original white level, the host 200 issuesthe commands 1915/1916 “set white level reference value” and the command1917 “execute setting of the white level reference” to replace the whitelevel reference value with the original white level reference value inSRAM 907 in the scan head cartridge 800. Finally, at step 2210, theclear sheet correction flag F2 is set to “0.” A normal scanningoperation is performed at step 2211 and completed at step 2212.

[0104] According to the embodiment of the present invention, the scanhead cartridge is designed to replace the print head cartridge on thecarriage of the printer/scanner block that prints an image on arecording medium. Thus, the printer/scanner block in the device works asan image scanner. -Based on the principle that processing the read imageis performed relative to the white level reference data, the devicepredicts data degradation due to the variation of reflectance of theoriginal attributed to transmissivity of the clear sheet and modifiesthe white level reference value in software before starting the actualimage reading. A single cycle of this correction process is performedprior to the use of the clear sheet, and thereafter, modified whitelevel reference data is used to correct the read data.

[0105] In the printer/scanner block that allows the scan head cartridgeto replace the print head cartridge, once the clear sheet is subjectedto the white level reference measurement, it is not necessary to measurethe white level any more thereafter. Furthermore, data correction isperformed without slowing down the reading speed (prolonging theaccumulation time).

[0106] In the printer/scanner block featuring a compact and low-costdesign, the host is capable of modifying the white level reference datain the scan head cartridge when a clear sheet is used. This arrangementeliminates the need for the white level reference value measurement thatwould be otherwise needed at each scanning operation, and further incursno slowdown in the scanning speed. The white level reference value maybe corrected not only to meet the clear sheet condition but also tocomply with a diversity of original document conditions.

What is claimed is:
 1. An image processing device having a slidablecarriage comprising a read cartridge that is mounted on the carriageduring use, said cartridge comprising: photoelectric converter means foroptically reading an image from an original document and converting theimage into an image signal; and memory means for storing reference datathat is used to correct the image signal output by the photoelectricconverter means.
 2. An image processing device according to claim 1,wherein the cartridge further comprises a light source for illuminatingthe original document.
 3. An image processing device according to claim2, wherein the cartridge further comprises optical means for guiding thelight ray reflected off the original document illuminated by the lightsource, to the photoelectric converter means.
 4. An image processingdevice according to claim 3, wherein the cartridge further comprisesamplifier means for amplifying the image signal output from thephotoelectric converter means.
 5. An image processing device accordingto claim 4, wherein the cartridge further comprises A/D converter meansfor A/D converting the image signal from the photoelectric convertermeans into a digital signal.
 6. An image processing device according toclaim 5, wherein the cartridge further comprises controller means forcontrolling the reference for the A/D converter means based on thereference data.
 7. An image processing device according to claim 1,wherein the reference data is white level reference data.
 8. An imageprocessing device according to claim 1, wherein the reference data isoffset data.
 9. An image processing system comprising: a control device;and an image processing device connected to and controlled by thecontrol device, said image processing device having a slidable carriage,comprising a read cartridge that is mounted on the carriage during use,said cartridge comprising: photoelectric converter means for opticallyreading an image from an original document and converting the image intoan image signal, and memory means for storing reference data that isused to correct the image signal output by the photoelectric convertermeans.
 10. An image processing system according to claim 9, wherein thecartridge further comprises a light source for illuminating the originaldocument.
 11. An image processing system according to claim 10, whereinthe cartridge further comprises optical means for guiding the light rayreflected off the original document illuminated by the light source, tothe photoelectric converter means.
 12. An image processing systemaccording to claim 11, wherein the cartridge further comprises amplifiermeans for amplifying the image signal output from the photoelectricconverter means.
 13. An image processing system according to claim 12,wherein the cartridge further comprises A/D converter means for A/Dconverting the image signal from the photoelectric converter means intoa digital signal.
 14. An image processing system according to claim 13,wherein the cartridge further comprises controller means for controllingthe reference for the A/D converter means based on the reference data.15. An image processing system according to claim 9, wherein the controldevice modifies the reference data stored in the memory means.
 16. Animage processing system according to claim 15, wherein the controldevice modifies the reference data based on the reading condition of thephotoelectric converter means.
 17. An image processing system accordingto claim 16 further comprises a holding member for holding the originaldocument, wherein the control device modifies the reference data whenthe photoelectric converter means reads the original document held bythe holding member.
 18. An image processing system according to claim16, wherein the control device modifies the reference data based on anaccumulation time of the photoelectric converter means.
 19. An imageprocessing system according to claim 16, wherein the control devicemodifies the reference data based on a resolution of the photoelectricconverter means.
 20. An image processing system according to claim 9,wherein the image processing device further comprises a print headcartridge.
 21. An image processing system according to claim 20, whereinone of the read cartridge and the print cartridge is selectively mountedon the carriage.
 22. An image processing system according to claim 9,wherein the reference data is white level reference data.
 23. An imageprocessing system according to claim 9, wherein the reference data isoffset data.